Table 3-5.—Minimum Amendment Criteria

that may require an amended TAF. Table 3-5 is a summary of minimum amendment criteria. More stringent amendment criteria may be established locally. The actual time that the amendment is completed for transmission is the last element encoded. For example, an amendment completed at 2130 UTC would have as the last element "AMD 2130." Not all, but most aviation weather offices are equipped with a PMSV voice radio. PMSV radio is used to pass updated weather observations and forecasts to aircraft in flight and to receive pilot-reported, flight- level, weather observations or pilot reports (PIREPs). The duty observer is normally assigned the responsibility to transmit and receive traffic over the PMSV radio. In the next section, we will discuss the PIREP code. Q1. Q2. Q3. Q4. Q5. REVIEW QUESTIONS What instruction governs the use of the Terminal Aerodrome Forecast (TAF) code for Navy and Marine Corps activities? What are the standard synoptic times for the transmission of TAFs and what is the valid forecast period? What cloud genus is always reported as a separate group for element N_sN_sN_sh_sh_sh_s of the TAF code? When is the abbreviation "WSCONDS" used in the TAF code? How should light icing from 6,000 to 10,000 feet be encoded in a TAF? Table 3-5.—Minimum Amendment Criteria Minimum Amendment Criteria Ceilings and Visibilities Whenever ceilings and/or visibilities are observed or are later forecast to increase to, equal or exceed, or decrease to less than any of the following: Ceiling Visibility 3,000 ft 4,800 meters 1,000 ft 1,600 meters 200 ft 800 meters Surface Winds Wind speed change of 10 knots or more. Directional change of 30° or more when mean wind or gusts are in excess of 15 knots. Winds speed or directional change resulting in change of active runway. Thunderstorm or Tornadic Activity Thunderstorm or tornadic activity was not forecast to occur, but later occurs or is expected to occur. Thunderstorm or tornadic activity was forecast, but later is not expected. Precipitation Precipitation that will affect safety of flight, including runway braking action, is occurring or is forecast to occur, of if forecast, is no longer expected. Non-Convective, Low-Level Wind Shear Low-Level Wind Shear is occurring or forecast to occur, or if forecast, is no longer expected. Q N H Whenever the observed altimeter falls below, or is expected to fall below the original forecast. 3-4